I've just changed my engine after the last one seized.
Now im not 100% that all the plugs and pipes are in the correct place.
When u start the car it won't idle.
At first u can rev it up but then you can push the accelerator and the revs hardly change and if u try and drive it u can barely move.

Any ideas?

 

It sounds like a clogged cat. Did they reuse plugs, coils and wires?

 

Did a Mazda dealership installed the engine or another auto shop? If its a new engine, and everything is installed correctly, then it shouldn't have any problems whatsoever, unless the catalytic is clogged up...

 

I put the engine in after a garage took it out.
New plugs, same coils and harness.
It appears to be going in to limp mode

 

It will idle on first turn over and continue to idle.
When u put your foot on the clutch thats when it dies

 

You put the engine by yourself? I'm not an expert on putting an engine, but i think you did not install it correctly or in specification...